Measurements of electric energy for billing purposes are known to be performed by meters capable of making measurements for different times of use or consumption basis so that different billing rates can be applied for electric energy used during different time intervals of each day. Earlier meters of the so-called time of day type utilize an induction watthour meter movement with multi-dial registers for selectively engaging separate register dials under the control of a mechanical clock mechanism. Many prior art multirate or time of day meters are fixed as to the electric energy parameter measurements that can be made and have limited flexibility for establishing different measuring time intervals. Typically, the only differences of daily measuring time schedules are provided between a weekday rate and a weekend. There are often considerable time and date cyclic variations in the demand for electric power supplied by an electric utility. It is a general object in the time of day type of meters to correlate the time intervals wherein different levels of power demand are occurring in an electric utility distribution system with the different categories of electricity usage measuring times. The electric power demand can vary on the basis of not only the days of the week but also vary differently on either Saturdays or Sundays, holidays and/or yearly seasonal basis, for example, winter seasons have earlier darkness and electric heating loads dominating demand while summer seasons have later darkness and electric air conditioning loads dominating demand.
Accordingly, it is desirable to have an AC electric energy meter which is capable of providing multiple measuring functions for totalizing and indicating different parameters of the consumption of AC electric energy and to totalize such parameters in different measuring time categories during each day of measurement. Such meters must permit wide flexibility for multirate billing for electric energy consumption and ease of making changes between the different parameters to be measured and the schedules for making the measurements. The use of such meters is often effective in reducing peak demands of electric energy usage and facilitates conservation in the use of electric energy.
The application of solid state electronic circuits and devices to time of day electric energy measurements affords greater flexibility in increasing the number of electric energy measurement parameters that may be made and increased flexibility in rate selection schedules possible for the electric energy billing operation than was afforded by earlier primarily electromechanical meters. The use of such solid state electronic circuits and devices present a number of different considerations so that the meters remain with the same operating capabilities of earlier electromechanical billing meters in that they must be accurate, rugged and reliable in operating in outdoor environments subject to wide variations in environmental temperature extremes and remain compact in size, capable of being assembled and manufactured by mass production techniques and have acceptable cost. High accuracy in both measuring and time and date recording operations is necessary while utilizing a minimum number of circuits for maintaining an optimum size and operation at acceptable power supply levels. The meter must be secure from tampering and alteration of the operation thereof, require minimum service and maintenance, and be further capable of operating for extended time under battery power during the power outage conditions of the electric energy quantity being measured. The aforementioned requirements and considerations are maintained in providing the programmable time registering AC electric energy meter of this invention as described briefly hereinafter.